Metal granulation in water is a well-established method for rapid solidification of liquid metal into a medium sized product form. The Granshot® process has been developed for the direct production of ready to use material for the steel industry. The known apparatus is disclosed in FIG. 1. The molten metal is directed from a tundish to a refractory target, which is denoted spray head in FIG. 1. The metal strikes the target, split up and is radially distributed over the cooling water in the tank. The droplets solidify in the tank and are recovered from the bottom of the tank. The size of the granules depends on several factors such as melt composition and impact conditions. The main fraction obtained lies within the size range of 5-25 mm. However, the amount of fines, defined as granules having a maximum dimension of ≤8 mm may be as high as 20%. The principles of this method are disclosed in EP 402 665 and U.S. Pat. No. 3,888,956.
U.S. Pat. No. 4,402,884 discloses a method of granulating using a rotating disc. The main part of the granules obtained according to this method has a size of less than 10 mm.
Although the grain sizes obtained by the above mentioned method allow a rapid dissolution of the granular metal in a steel melt there is a drawback in that there are limited possibilities to adjust the mean grain size and the grain size distribution.
EP 522 844 discloses a method of producing metal granules by pouring a metal stream into a liquid cooling bath. U.S. Pat. No. 6,287,362 discloses a method of producing metal lumps having a characteristic dimension of 20-100 mm by introducing a molten metal stream into a stream of water. Drawbacks associated with these methods are long dissolution times for the coarse material and a wide particle size distribution.